The proper maintenance of industrial components involves many activities and a variety of scientific disciplines. For example, the maintenance of steam generators of a nuclear power plant involves the fields of nondestructive testing, chemical and mechanical cleaning, robotics, mechanical engineering, metallurgy, fracture analysis, welding and radiological protection. Typically a steam generator is inspected and cleaned during a plant outage. If the inspection reveals degradation or damage to the component, repair activities are undertaken. Between outages, the history of inspection results and repair activities involving the steam generator may be evaluated in an effort to specify inspections for the next outage and to predict the repair activities which may be required.
The maintenance of a nuclear steam generator is an expensive and time consuming task. Often the steam generator activities are on the critical path for returning the plant to power operation. Delays can occur during many phases of the outage activities. For example, nondestructive inspection data, such as eddy current test data of steam generator tubes, must be analyzed to determine if there are discontinuities or flaws in the component. If the data includes any sort of anomaly, a diagnosis must be performed to determine if the anomaly is significant enough to prevent the continued operation of the component. When there is a history of inspections for the steam generator or a family of similar components in service at other locations, it is often helpful to compare the data being analyzed to that taken previously, and to identify any similarities or trends which may be present. Once a degradation mechanism is understood and properly characterized, a repair program may be prepared and implemented. The conservative repair option for nuclear steam generator tubes is to remove the tube from service by plugging. However, this option reduces the operating margin of the component, and it is not the most desirable option over the long term. Due to the demands of the plant schedule, it is often this most conservative option which is chosen, since the time necessary to properly analyze other options is not available.